In the prior art, there are wiring substrates for mounting electronic components such as semiconductor chips. As such wiring substrates, there are coreless type wiring substrates having no core substrate. The coreless type wiring substrates are manufactured based on forming desired build-up wiring layers on a supporting member and then removing the supporting member. A related art is disclosed in Japanese Laid-open Patent Publication No. 11-289163, Japanese Laid-open Patent Publication No. 2008-153580, and Japanese Laid-open Patent Publication No. 2009-88429.